Zinc + Warm Or Cold Roof

[Matt60]

I'm try to plan several headaches ahead and headache number 5-ish is my roof. I was i'll advised about the costs of a zinc roof which I picked (and still like) and which is now part of the detailed planning and discharged materials. My plot is next to 2 others all with the same condition and the planners will only let us change if all 3 do and that is not going to happen. I don't really mind tbh as I do prefer it.

 

What I need to work out is whether to go for a warm or cold roof, I'm told that there isn't much difference in the U value but that the cold roof will be several thousand less as it requires much less materials. The house is storey and a half and so at 1800mm from the upstairs floor, the roof starts to make it's makes it's presence felt, if that makes sense?

 

I'd like to know the pro and cons of both roof systems, and if one has better sound deadening qualities than the other, and if the cost difference between cold and warm is correct.

 

I've attached a cross-section of just one part of the house to make clearer how the roof interacts with the walls.Roof section example.pdf

 

Thanks in advance for your help.

[GraemeHM]

We’re just getting to the final stages of our extension. I had a similar question when we first started. The issue is condensation forming on the underside of the metal. I spoke to lots of people including a very knowledgable guy from VM Zinc who said. “You can do either (cold vented, warm unvented) especially if it’s a new build and you do everything properly and use the correct materials. But, given the choice he would say that a cold roof I.e vented is more forgiving in the long run”.

 

There is lots of detailed discussions on here about the pros and cons. 

 

In the end I went for an aluminium standing seam roof on a cold vented roof. It looks the same although there subtle differences for the installer. They do the same job, but the aluminium is cheaper and doesn’t suffer with the “possibility” of corrosion.

 

Noise is hard to compare like for like. I had heard that cold vented could be slightly noisier, but to be honest our experience so far (and my god we’ve had some rain down here in Devon during May) is that the roof buildup needed for BC soaks up the noise really well.

[SimonD]

16 hours ago, Matt60 said:

I'd like to know the pro and cons of both roof systems, and if one has better sound deadening qualities than the other, and if the cost difference between cold and warm is correct.

 

The simple difference is in condensation risk. There is greater risk with the warm roof. The difference in price is not just with materials but with labour as if you're constructing a warm roof, the metal roofing contractor should really do the roof buildup and detailing because most building contractors won't have a clue what's needed.

[Matt60]

Brilliant, thank you for your replies - very much appreciated.